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Dirven BCJ, Homberg JR, Kozicz T, Henckens MJAG. Epigenetic programming of the neuroendocrine stress response by adult life stress. J Mol Endocrinol 2017; 59:R11-R31. [PMID: 28400482 DOI: 10.1530/jme-17-0019] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 03/17/2017] [Indexed: 12/11/2022]
Abstract
The hypothalamic-pituitary-adrenal (HPA) axis is critically involved in the neuroendocrine regulation of stress adaptation, and the restoration of homeostasis following stress exposure. Dysregulation of this axis is associated with stress-related pathologies like major depressive disorder, post-traumatic stress disorder, panic disorder and chronic anxiety. It has long been understood that stress during early life can have a significant lasting influence on the development of the neuroendocrine system and its neural regulators, partially by modifying epigenetic regulation of gene expression, with implications for health and well-being in later life. Evidence is accumulating that epigenetic plasticity also extends to adulthood, proposing it as a mechanism by which psychological trauma later in life can long-lastingly affect HPA axis function, brain plasticity, neuronal function and behavioural adaptation to neuropsychological stress. Further corroborating this claim is the phenomenon that these epigenetic changes correlate with the behavioural consequences of trauma exposure. Thereby, epigenetic modifications provide a putative molecular mechanism by which the behavioural phenotype and transcriptional/translational potential of genes involved in HPA axis regulation can change drastically in response to environmental challenges, and appear an important target for treatment of stress-related disorders. However, improved insight is required to increase their therapeutic (drug) potential. Here, we provide an overview of the growing body of literature describing the epigenetic modulation of the (primarily neuroendocrine) stress response as a consequence of adult life stress and interpret the implications for, and the challenges involved in applying this knowledge to, the identification and treatment of stress-related psychiatric disorders.
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MESH Headings
- Animals
- Anxiety/genetics
- Anxiety/metabolism
- Anxiety/physiopathology
- Brain/metabolism
- Brain/physiopathology
- DNA Methylation
- Depressive Disorder, Major/genetics
- Depressive Disorder, Major/metabolism
- Depressive Disorder, Major/physiopathology
- Epigenesis, Genetic
- Histones/genetics
- Histones/metabolism
- Homeostasis
- Humans
- Hypothalamo-Hypophyseal System/metabolism
- Hypothalamo-Hypophyseal System/physiopathology
- MicroRNAs/genetics
- MicroRNAs/metabolism
- Neurons/metabolism
- Neurons/pathology
- Neurotransmitter Agents/metabolism
- Pituitary-Adrenal System/metabolism
- Pituitary-Adrenal System/physiopathology
- Receptors, Glucocorticoid/genetics
- Receptors, Glucocorticoid/metabolism
- Receptors, Mineralocorticoid/genetics
- Receptors, Mineralocorticoid/metabolism
- Stress, Psychological/genetics
- Stress, Psychological/metabolism
- Stress, Psychological/physiopathology
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Affiliation(s)
- B C J Dirven
- Department of AnatomyDonders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
- Department of Cognitive NeuroscienceDonders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - J R Homberg
- Department of Cognitive NeuroscienceDonders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - T Kozicz
- Department of AnatomyDonders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - M J A G Henckens
- Department of Cognitive NeuroscienceDonders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
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2
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Kroeze Y, Peeters D, Boulle F, van den Hove DLA, van Bokhoven H, Zhou H, Homberg JR. Long-term consequences of chronic fluoxetine exposure on the expression of myelination-related genes in the rat hippocampus. Transl Psychiatry 2016; 6:e779. [PMID: 27070407 PMCID: PMC4872416 DOI: 10.1038/tp.2016.60] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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3
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Olde Loohuis NFM, Kole K, Glennon JC, Karel P, Van der Borg G, Van Gemert Y, Van den Bosch D, Meinhardt J, Kos A, Shahabipour F, Tiesinga P, van Bokhoven H, Martens GJM, Kaplan BB, Homberg JR, Aschrafi A. Elevated microRNA-181c and microRNA-30d levels in the enlarged amygdala of the valproic acid rat model of autism. Neurobiol Dis 2015; 80:42-53. [PMID: 25986729 DOI: 10.1016/j.nbd.2015.05.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 04/14/2015] [Accepted: 05/10/2015] [Indexed: 11/17/2022] Open
Abstract
Autism spectrum disorders are severe neurodevelopmental disorders, marked by impairments in reciprocal social interaction, delays in early language and communication, and the presence of restrictive, repetitive and stereotyped behaviors. Accumulating evidence suggests that dysfunction of the amygdala may be partially responsible for the impairment of social behavior that is a hallmark feature of ASD. Our studies suggest that a valproic acid (VPA) rat model of ASD exhibits an enlargement of the amygdala as compared to controls rats, similar to that observed in adolescent ASD individuals. Since recent research suggests that altered neuronal development and morphology, as seen in ASD, may result from a common post-transcriptional process that is under tight regulation by microRNAs (miRs), we examined genome-wide transcriptomics expression in the amygdala of rats prenatally exposed to VPA, and detected elevated miR-181c and miR-30d expression levels as well as dysregulated expression of their cognate mRNA targets encoding proteins involved in neuronal system development. Furthermore, selective suppression of miR-181c function attenuates neurite outgrowth and branching, and results in reduced synaptic density in primary amygdalar neurons in vitro. Collectively, these results implicate the small non-coding miR-181c in neuronal morphology, and provide a framework of understanding how dysregulation of a neurodevelopmentally relevant miR in the amygdala may contribute to the pathophysiology of ASD.
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Affiliation(s)
- N F M Olde Loohuis
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - K Kole
- Department of Neuroinformatics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - J C Glennon
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - P Karel
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - G Van der Borg
- Department of Neuroinformatics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - Y Van Gemert
- Department of Neuroinformatics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - D Van den Bosch
- Department of Neuroinformatics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - J Meinhardt
- Department of Neuroinformatics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - A Kos
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - F Shahabipour
- Department of Neuroinformatics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - P Tiesinga
- Department of Neuroinformatics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands
| | - H van Bokhoven
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands; Department of Human Genetics, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - G J M Martens
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition and Behavior, Nijmegen Centre for Molecular Life Sciences (NCMLS), Radboud University Nijmegen, Nijmegen, The Netherlands
| | - B B Kaplan
- Laboratory of Molecular Biology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - J R Homberg
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - A Aschrafi
- Department of Neuroinformatics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands.
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van der Doelen RHA, Deschamps W, D'Annibale C, Peeters D, Wevers RA, Zelena D, Homberg JR, Kozicz T. Early life adversity and serotonin transporter gene variation interact at the level of the adrenal gland to affect the adult hypothalamo-pituitary-adrenal axis. Transl Psychiatry 2014; 4:e409. [PMID: 25004389 PMCID: PMC4119224 DOI: 10.1038/tp.2014.57] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Revised: 05/06/2014] [Accepted: 05/22/2014] [Indexed: 01/17/2023] Open
Abstract
The short allelic variant of the serotonin transporter (5-HTT) promoter-linked polymorphic region (5-HTTLPR) has been associated with the etiology of major depression by interaction with early life stress (ELS). Furthermore, 5-HTTLPR has been associated with abnormal functioning of the stress-responsive hypothalamo-pituitary-adrenal (HPA) axis. Here, we examined if, and at what level, the HPA-axis is affected in an animal model for ELS × 5-HTTLPR interactions. Heterozygous and homozygous 5-HTT knockout rats and their wild-type littermates were exposed daily at postnatal days 2-14 to 3 h of maternal separation. When grown to adulthood, plasma levels of adrenocorticotropic hormone (ACTH), and the major rat glucocorticoid, corticosterone (CORT), were measured. Furthermore, the gene expression of key HPA-axis players at the level of the hypothalamus, pituitary and adrenal glands was assessed. No 5-HTT genotype × ELS interaction effects on gene expression were observed at the level of the hypothalamus or pituitary. However, we found significant 5-HTT genotype × ELS interaction effects for plasma CORT levels and adrenal mRNA levels of the ACTH receptor, such that 5-HTT deficiency was associated under control conditions with increased, but after ELS with decreased basal HPA-axis activity. With the use of an in vitro adrenal assay, naïve 5-HTT knockout rats were furthermore shown to display increased adrenal ACTH sensitivity. Therefore, we conclude that basal HPA-axis activity is affected by the interaction of 5-HTT genotype and ELS, and is programmed, within the axis itself, predominantly at the level of the adrenal gland. This study therefore emphasizes the importance of the adrenal gland for HPA-related psychiatric disorders.
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Affiliation(s)
- R H A van der Doelen
- Department of Anatomy, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands,Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands,Department of Anatomy, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Geert Grooteplein 21 (route 126), 6525 EZ Nijmegen, The Netherlands. E-mail:
| | - W Deschamps
- Department of Cellular Animal Physiology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - C D'Annibale
- Department of Cellular Animal Physiology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - D Peeters
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands,Department of Cellular Animal Physiology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - R A Wevers
- Department of Laboratory Medicine, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - D Zelena
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - J R Homberg
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - T Kozicz
- Department of Anatomy, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
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5
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van der Doelen RHA, Kozicz T, Homberg JR. Adaptive fitness; early life adversity improves adult stress coping in heterozygous serotonin transporter knockout rats. Mol Psychiatry 2013; 18:1244-5. [PMID: 23319004 DOI: 10.1038/mp.2012.186] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- R H A van der Doelen
- 1] Department of Cellular Animal Physiology, Radboud University Nijmegen, Nijmegen, The Netherlands [2] Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands
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6
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Olivier JDA, Blom T, Arentsen T, Homberg JR. The age-dependent effects of selective serotonin reuptake inhibitors in humans and rodents: A review. Prog Neuropsychopharmacol Biol Psychiatry 2011; 35:1400-8. [PMID: 20883714 DOI: 10.1016/j.pnpbp.2010.09.013] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 08/07/2010] [Accepted: 09/15/2010] [Indexed: 01/27/2023]
Abstract
The selective serotonin reuptake inhibitor (SSRI) Prozac® (fluoxetine) is widely prescribed for the treatment of depression and anxiety-related disorders. While extensive research has established that fluoxetine is safe for adults, safety is not guaranteed for (unborn) children and adolescents. Some clinical studies have reported adverse outcomes, such as premature birth, neonatal cardiovascular abnormalities, and pulmonary hypertension in children whose mothers used SSRIs during pregnancy. In addition, several reports show that adolescent fluoxetine treatment increases risk for suicidal behavior. Despite these studies, fluoxetine is not contraindicated in the treatment of depressed pregnant women and adolescents. Longitudinal research in humans is limited because of ethical reasons and time constraints, and to overcome these limitations, rodents are used to increase insight in the age-dependent effects of fluoxetine exposure. It has been established that neonatal and adolescent fluoxetine exposure leads to paradoxical anxiety- and depression-like features in later life of rats and mice, although in some studies adolescent fluoxetine exposure was without effects. These age-dependent outcomes of fluoxetine may be explained by serotonin's neurotrophic effects, which may vary according to the developmental stage of the brain due to epigenetic modifications. Here we review the existing evidence for the age-dependent effects of fluoxetine in humans and rodents, address the gaps in our current knowledge and propose directions for future research. Given the overlap between human and rodent findings, rodents provide heuristic value in further research on the age-dependent effects of SSRIs.
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Affiliation(s)
- J D A Olivier
- Donders Institute for Brain, Cognition, and Behaviour, Centre for Neuroscience, Dept. of Cognitive Neuroscience, Radboud University Nijmegen Medical Centre, Geert Grooteplein 21, 6525 GA Nijmegen, The Netherlands
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7
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Neumann ID, Wegener G, Homberg JR, Cohen H, Slattery DA, Zohar J, Olivier JDA, Mathé AA. Animal models of depression and anxiety: What do they tell us about human condition? Prog Neuropsychopharmacol Biol Psychiatry 2011; 35:1357-75. [PMID: 21129431 DOI: 10.1016/j.pnpbp.2010.11.028] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Revised: 10/24/2010] [Accepted: 11/19/2010] [Indexed: 01/07/2023]
Abstract
While modern neurobiology methods are necessary they are not sufficient to elucidate etiology and pathophysiology of affective disorders and develop new treatments. Achievement of these goals is contingent on applying cutting edge methods on appropriate disease models. In this review, the authors present four rodent models with good face-, construct-, and predictive-validity: the Flinders Sensitive rat line (FSL); the genetically "anxious" High Anxiety-like Behavior (HAB) line; the serotonin transporter knockout 5-HTT(-/-) rat and mouse lines; and the post-traumatic stress disorder (PTSD) model induced by exposure to predator scent, that they have employed to investigate the nature of depression and anxiety.
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Affiliation(s)
- I D Neumann
- Dept of Behavioural Neuroendocrinology, Faculty of Biology and Preclinical Medicine, University of Regensburg, Regensburg, Germany
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8
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Olivier JDA, Jans LAW, Blokland A, Broers NJ, Homberg JR, Ellenbroek BA, Cools AR. Serotonin transporter deficiency in rats contributes to impaired object memory. Genes, Brain and Behavior 2009; 8:829-34. [DOI: 10.1111/j.1601-183x.2009.00530.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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9
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Homberg JR, Mul JD, de Wit E, Cuppen E. Complete knockout of the nociceptin/orphanin FQ receptor in the rat does not induce compensatory changes in mu, delta and kappa opioid receptors. Neuroscience 2009; 163:308-15. [PMID: 19527777 DOI: 10.1016/j.neuroscience.2009.06.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2009] [Revised: 06/07/2009] [Accepted: 06/09/2009] [Indexed: 11/29/2022]
Abstract
The nociceptin/orphanin FQ (N/OFQ) opioid peptide receptor (NOPr) is a new member of the opioid receptor family consisting of mu, delta and kappa opioid receptors. The anti-opioid properties of its endogenous ligand, N/OFQ provide the receptor interesting potentials in symptoms and processes related to drug addiction, learning and memory, anxiety and depression, and nociception. Using target-selected N-ethyl-N-nitrosourea (ENU)-driven mutagenesis we recently generated a rat model bearing a premature stop codon in the opioid-like receptor (oprl1) gene, and here we describe the primary characterization of this novel model. Data revealed that [(3)H]N/OFQ binding to brain slices was completely absent in rats homozygous for the premature stop codon (oprl1(-/-)). Heterozygous rats displayed an intermediate level of NOPr binding. Oprl1 receptor transcript levels, as determined by Northern blot analysis, were reduced by approximately 50% in oprl1(-/-) rats compared to wild-type controls (oprl1(+/+)), and no alternative spliced transcripts were observed. Quantitative autoradiographic mapping of mu, delta and kappa opioid receptors using [(3)H]DAMGO, [(3)H]deltorphin and [(3)H]CI-977, respectively, did not show any changes in opioid receptor binding. In conclusion, we present a novel mutant rat lacking NOPr without compensatory changes in mu, delta and kappa opioid receptors. We anticipate that this mutant rat will have heuristic value to further understand the function of NOPr.
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MESH Headings
- Alternative Splicing/genetics
- Analgesics, Opioid/metabolism
- Animals
- Binding, Competitive/genetics
- Brain/drug effects
- Brain/metabolism
- Brain Chemistry/drug effects
- Brain Chemistry/genetics
- Codon, Nonsense/genetics
- Disease Models, Animal
- Gene Knockout Techniques
- Opioid Peptides/genetics
- Organ Culture Techniques
- Radioligand Assay
- Rats
- Rats, Wistar
- Receptors, Opioid/genetics
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, kappa/metabolism
- Receptors, Opioid, mu/metabolism
- Tritium
- Nociceptin Receptor
- Nociceptin
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Affiliation(s)
- J R Homberg
- Hubrecht Institute and University Medical Center Utrecht, Uppsalalaan 8, 3584 CT, Utrecht, The Netherlands
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10
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Kalueff AV, Olivier JDA, Nonkes LJP, Homberg JR. Conserved role for the serotonin transporter gene in rat and mouse neurobehavioral endophenotypes. Neurosci Biobehav Rev 2009; 34:373-86. [PMID: 19698744 DOI: 10.1016/j.neubiorev.2009.08.003] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2009] [Revised: 08/12/2009] [Accepted: 08/13/2009] [Indexed: 10/20/2022]
Abstract
The serotonin transporter knockout (SERT(-/-)) mouse, generated in 1998, was followed by the SERT(-/-) rat, developed in 2006. The availability of SERT(-/-) rodents creates the unique possibility to study the conservation of gene function across species. Here we summarize SERT(-/-) mouse and rat data, and discuss species (dis)similarities in neurobehavioral endophenotypes. Both SERT(-/-) rodent models show a disturbed serotonergic system, altered nociception, higher anxiety, decreased social behavior, as well as increased negative emotionality, behavioral inhibition and decision making. Used to model a wide range of psychiatric disorders, SERT(-/-) rodents may be particularly valuable in research on neurodevelopmental disorders such as depression, anxiety, and possibly autism. We conclude that SERT function is conserved across mice and rats and that their behavioral profile arises from common neurodevelopmental alterations. Because mice and rats have species-specific characteristics that confer differential research advantages, a comparison of the two models has heuristic value in understanding the mechanisms and behavioral outcome of SERT genetic variation in humans.
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Affiliation(s)
- A V Kalueff
- Department of Pharmacology, Tulane University Medical School, New Orleans, LA 70112, USA
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11
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Olivier JDA, Van Der Hart MGC, Van Swelm RPL, Dederen PJ, Homberg JR, Cremers T, Deen PMT, Cuppen E, Cools AR, Ellenbroek BA. A study in male and female 5-HT transporter knockout rats: an animal model for anxiety and depression disorders. Neuroscience 2008; 152:573-84. [PMID: 18295409 DOI: 10.1016/j.neuroscience.2007.12.032] [Citation(s) in RCA: 168] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Revised: 12/24/2007] [Accepted: 12/28/2007] [Indexed: 12/16/2022]
Abstract
Human studies have shown that a reduction of 5-HT transporter (SERT) increases the vulnerability for anxiety and depression. Moreover, women are more vulnerable to develop depression and anxiety disorders than men. For that reason we hypothesized that homozygous 5-HT transporter knockout rat (SERT(-/-)) models, especially female, are valuable and reliable animal models for humans with an increased vulnerability for anxiety- and depression-related disorders. As rats are extensively used in neuroscience research, we used the unique 5-HT transporter knockout rat, that was recently generated using N-ethyl-N-nitrosurea (ENU) -driven mutagenesis, to test this hypothesis. Behavioral testing revealed that male and female SERT(-/-) rats spent less time in the center of the open field and spent less time on the open arm of the elevated plus maze compared with wild-type 5-HT transporter knockout rats (SERT(+/+)). In the novelty suppressed feeding test, only male SERT(-/-) rats showed a higher latency before starting to eat in a bright novel arena compared with SERT(+/+) controls. Both male and female SERT(-/-) rats showed a higher escape latency from their home cage than SERT(+/+) littermates. Moreover, SERT(-/-) rats were less mobile in the forced swim test, and sucrose consumption was reduced in SERT(-/-) rats relative to SERT(+/+) rats. Both effects were sex-independent. Neurochemically, basal extracellular 5-HT levels were elevated to a similar extent in male and female SERT(-/-) rats, which was not influenced by the selective 5-HT reuptake inhibitor citalopram. 5-HT immunostaining revealed no difference between SERT(+/+) and SERT(-/-) rats in the dorsal raphe nuclei, in both males and females. These findings demonstrate that SERT(-/-) rats show anxiety and depression-related behavior, independent of sex. Genetic inactivation of the SERT has apparently such a great impact on behavior, that hardly any differences are found between male and female rats. This knockout rat model may provide a valuable model to study anxiety- and depression-related disorders in male and female rats.
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Affiliation(s)
- J D A Olivier
- Department of Cognitive Neuroscience: Psychoneuropharmacology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
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12
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Homberg JR, Olivier JDA, Smits BMG, Mul JD, Mudde J, Verheul M, Nieuwenhuizen OFM, Cools AR, Ronken E, Cremers T, Schoffelmeer ANM, Ellenbroek BA, Cuppen E. Characterization of the serotonin transporter knockout rat: a selective change in the functioning of the serotonergic system. Neuroscience 2007; 146:1662-76. [PMID: 17467186 DOI: 10.1016/j.neuroscience.2007.03.030] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Revised: 03/14/2007] [Accepted: 03/19/2007] [Indexed: 10/23/2022]
Abstract
Serotonergic signaling is involved in many neurobiological processes and disturbed 5-HT homeostasis is implicated in a variety of psychiatric and addictive disorders. Here, we describe the functional characterization of the serotonin transporter (SERT) knockout rat model, that is generated by N-ethyl-N-nitrosurea (ENU)-driven target-selected mutagenesis. Biochemical characterization revealed that SERT mRNA and functional protein are completely absent in homozygous knockout (SERT-/-) rats, and that there is a gene dose-dependent reduction in the expression and function of the SERT in heterozygous knockout rats. As a result, 5-HT homeostasis was found to be severely affected in SERT-/- rats: 5-HT tissue levels and depolarization-induced 5-HT release were significantly reduced, and basal extracellular 5-HT levels in the hippocampus were ninefold increased. Interestingly, we found no compensatory changes in in vitro activity of tryptophan hydroxylase and monoamine oxidase, the primary enzymes involved in 5-HT synthesis and degradation, respectively. Similarly, no major adaptations in non-serotonergic systems were found, as determined by dopamine and noradrenaline transporter binding, monoamine tissue levels, and depolarization-induced release of dopamine, noradrenaline, glutamate and GABA. In conclusion, neurochemical changes in the SERT knockout rat are primarily limited to the serotonergic system, making this novel rat model potentially very useful for studying the behavioral and neurobiological consequences of disturbed 5-HT homeostasis.
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Affiliation(s)
- J R Homberg
- Hubrecht Laboratory, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands
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13
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Homberg JR, Arends B, Wardeh G, Raasø HS, Schoffelmeer ANM, de Vries TJ. Individual differences in the effects of serotonergic anxiolytic drugs on the motivation to self-administer cocaine. Neuroscience 2004; 128:121-30. [PMID: 15450359 DOI: 10.1016/j.neuroscience.2004.05.048] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2004] [Indexed: 11/20/2022]
Abstract
Numerous clinical studies have indicated that lifetime anxiety is highly prevalent in drug addicts. In the treatment of drug abuse, dually diagnosed drug addicts may benefit from pharmacological intervention strategies that alleviate the psychiatric symptomatology. We have previously shown that rats with different coping strategies in a stressful environment show strong differences in the motivation to self-administer cocaine. That is, cocaine self-administration under a progressive ratio (PR) schedule of reinforcement was enhanced in high grooming (HG) rats as compared with low grooming (LG) rats. To identify the pharmacological basis of these differences, we tested the acute effects of several anxiolytic drugs on cocaine self-administration in HG and LG rats under a PR schedule of reinforcement. Chlordiazepoxide increased PR responding in both the HG and LG rats, while the selective corticotrophin releasing hormone 1 receptor antagonist R121919 had no effect on cocaine self-administration under the PR schedule. Interestingly, buspirone and fluoxetine decreased PR responding in HG rats only and thereby abolished the individual differences in PR responding between HG and LG rats. In support of the differential effects of the serotonergic drugs on PR responding in HG and LG rats, we found that the in vitro electrically evoked release of [3H]serotonin from mesocorticolimbic brain slices was reduced in the medial prefrontal cortex, substantia nigra and nucleus accumbens core, and increased in the nucleus accumbens shell of HG rats relative to LG rats. These findings show that serotonergic anxiolytics abolish the pre-existing individual differences in cocaine self-administration between HG and LG rats, which show differences in the reactivity of serotonergic neurons. This suggests that the effectiveness of pharmacological interference may depend on the neurochemical and motivational state of the individual.
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Affiliation(s)
- J R Homberg
- Graduate School Neuroscience Amsterdam, Research Institute Neurosciences Vrije Universiteit, Drug Abuse Program, Department of Medical Pharmacology, VU Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
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14
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Homberg JR, Wardeh G, Raasø HS, Schoffelmeer ANM, De Vries TJ. Neuroadaptive changes in mesocorticolimbic dopamine and acetylcholine neurons following cocaine or saline self-administration are dependent on pre-existing individual differences. Neuroscience 2003; 121:829-36. [PMID: 14580932 DOI: 10.1016/j.neuroscience.2003.07.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previously, we demonstrated that stress-induced self-grooming behaviour in rats predicted an enhanced motivation to self-administer cocaine as determined under a progressive ratio schedule of reinforcement. The enhanced motivation of high grooming (HG) rats was associated with a reduced reactivity of dopaminergic neurons in the medial prefrontal cortex and amygdala, but not nucleus accumbens. In the present study, we studied the effect of cocaine and saline self-administration on these pre-existing differences in neurochemical profile by determining the electrically evoked release of [3H]dopamine and [14C]acetylcholine from superfused slices of the nucleus accumbens shell and core, medial prefrontal cortex and amygdala of HG and low grooming (LG) rats. Although HG and LG rats did not differ in acquisition of cocaine and saline self-administration, both conditions induced substantially different neuroadaptations in these rats. Differences in depolarisation-induced dopamine and acetylcholine release were maintained in the medial prefrontal cortex, emerged in the nucleus accumbens and dissipated in the amygdala. These results indicate that altered reactivity of mesocorticolimbic dopaminergic and cholinergic neurons due to exposure to cocaine and environmental stimuli (saline) is dependent on pre-existing neurochemical differences and displays region-specificity. These pre-existing differences and the cocaine- and environmental-induced neuroadaptations seem to act in concert to produce an enhanced motivational state to self-administer cocaine.
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Affiliation(s)
- J R Homberg
- Research Institute Neurosciences Vrije Universiteit, Drug Abuse Program, Department of Medical Pharmacology, VU Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
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De Vries TJ, Shaham Y, Homberg JR, Crombag H, Schuurman K, Dieben J, Vanderschuren LJ, Schoffelmeer AN. A cannabinoid mechanism in relapse to cocaine seeking. Nat Med 2001; 7:1151-4. [PMID: 11590440 DOI: 10.1038/nm1001-1151] [Citation(s) in RCA: 347] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Treatment of cocaine addiction is hampered by high rates of relapse even after prolonged drug abstinence. This relapse to compulsive cocaine use can be triggered by re-exposure to cocaine, by re-exposure to stimuli previously associated with cocaine or by exposure to stress. In laboratory rats, similar events reinstate cocaine seeking after prolonged withdrawal periods, thus providing a model to study neuronal mechanisms underlying the relapse to cocaine. The endocannabinoid system has been implicated in a number of neuropsychiatric conditions, including drug addiction. The active ingredient of marijuana, Delta9-tetrahydrocannabinol, activates the mesolimbic dopamine (DA) reward system and has rewarding effects in preclinical models of drug abuse. We report here that the synthetic cannabinoid agonist, HU210 (ref. 13), provokes relapse to cocaine seeking after prolonged withdrawal periods. Furthermore, the selective CB1 receptor antagonist, SR141716A (ref. 14), attenuates relapse induced by re-exposure to cocaine-associated cues or cocaine itself, but not relapse induced by exposure to stress. These data reveal an important role of the cannabinoid system in the neuronal processes underlying relapse to cocaine seeking, and provide a rationale for the use of cannabinoid receptor antagonists for the prevention of relapse to cocaine use.
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Affiliation(s)
- T J De Vries
- Research Institute Neurosciences Vrije Universiteit, Department of Medical Pharmacology, VU Medical Center, Amsterdam, The Netherlands.
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Nestby P, Schoffelmeer AN, Homberg JR, Wardeh G, De Vries TJ, Mulder AH, Vanderschuren LJ. Bremazocine reduces unrestricted free-choice ethanol self-administration in rats without affecting sucrose preference. Psychopharmacology (Berl) 1999; 142:309-17. [PMID: 10208324 DOI: 10.1007/s002130050894] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
It has been postulated that opioid systems in the brain may play a role in ethanol reinforcement. In this respect, mu- and delta-opioid receptors may mediate the rewarding effects whereas kappa receptors are thought to mediate the aversive effects of opioids. Accordingly, long-acting benzomorphans such as bremazocine, that simultaneously act as mu and delta receptor antagonists and kappa receptor agonists may be particularly effective in reducing ethanol self-administration. Therefore, we studied the effect of bremazocine on oral ethanol self-administration in rats using a paradigm [unrestricted free-choice drinking of 10% (v/v) ethanol], previously shown to cause long-term neuroadaptations in the nucleus accumbens and caudate putamen. Bremazocine (0.1 mg/kg, once daily for five consecutive days) reduced ethanol drinking by about 50% during the active period of the animals, whereas the intake of sucrose (3-10% w/v) was affected neither in naive nor in ethanol-experienced rats. This effect of bremazocine appeared not to be secondary to its acute sedative effect or the slight increase in total fluid consumption. Unlike bremazocine, the selective kappa-opioid receptor agonist U50,488H (10 mg/kg, once daily) inhibited ethanol drinking only during the first of 5 treatment days and the opioid receptor antagonist naltrexone (0.3-10 mg/kg, once daily) only caused a modest (about 20%) suppression of ethanol drinking during the first hours after drug injection. Thus, bremazocine appears to be far more potent than the clinically applied drug naltrexone in this respect. Our data further support the role of opioid receptors in ethanol reinforcement and indicate that long-acting mixed-action opioids such as bremazocine may be useful as adjuvants for the clinical management of ethanol addiction.
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Affiliation(s)
- P Nestby
- Research Institute Neurosciences Vrije Universiteit, Department of Pharmacology, Free University, Medical Faculty, The Netherlands
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